- O Alienista
- O Andarilho das Sombras
- O beijo de Rudra
- O caderno azul de Jenny
- O Conde de Brass
- O Conde e a Artesã
- O Cão Negro de Clontarf
- O Despertar da Fúria
- O Evangelho do Engenheiro
- O festim dos corvos
- O Fidalgo Diabo
- O Fim do Mundo
- O gigante enterrado
- O Irmão Gêmeo do Falecido
- O Jardim Secreto - Nova Edição
- O mistério de Troia
- O Pássaro Pi-a-sa
- O Reino do Amaldiçoado
- O Retrato de Dorian Gray
- O Selo do Imperador
- O último sol poente
- O último tiro da Guanabara
- O'Reardon's Peace
- O'Taheiti Dreamin'
- Oak Seer
- Oath Bound: Book V of the Order of the Air
- Oath of a Warrior
- Obeah
- Obietnica Krwi
- Obras - Coleccion de Maximo Gorki
- Obras - Coleccion de Anatole France
- Obscura Legio
- Obsidian
- Ocean Gods, Roman Blades
- Ocean's Bride
- Ocean's Justice
- Ocean's Rise
- Ocean's War
- Ocean's Widow
- Oceania
- Od Magic
- Odem des Todes
- Odin lándzsája
- Odisseo - La forza dell'Amore
- Odysseus Fattens Calypso - A Weight Gain Story
- Of Careens, Swings, and Things
- Of Cats and Elfins
- Of Fate and Phantoms
- Of Gods, Kings and Heroes
- Of Human Hubris
- of Men and Dragons
- Of Noble Family
- Of Sentimental Value
- Of Sorrow and Such
- Of Trolls
- Offa's Bruid
- Office at Night
- Officer And Man
- Oh, Lucifer,: Fallen, Fallen, Fallen
- Oiling The Wheels
- Ojos color del tiempo
- Okami: A Little Red Riding Hood Retelling
- Oko Jelenia 1
- Oko jelenia 4
- Oko Jelenia 5
- Oko Jelenia 6
- Okrax
- Old Country Surprises
- Old French Romances Done into English (1896)
- Old Game, New Players (The Witch Who Came In From The Cold, Season 2 Episode 3)
- Old in Mischief (Tremontaine Season 2 Episode 2)
- Old Mommark's Tale
- Old Saint Paul's: A Tale of the Plague and the Fire
- Old Tom and the Old Tome
- Olde Robin Hood
- Ole Ohnefurcht: Und der Fluch des Tränenhügels (Überarbeitete und gekürzte Ausgabe)
- Olympian Confessions
- Omar's Well
- Ombria in Shadow
- Omega Marked
- Omina-Uvorix: The Legend
- Omnia
- OM—The Secret of Ahbor Valley
- On A Pale Horse
- On Armored Wings
- On Blazing Wings
- On Celestra’s Wings
- On Common Ground
- On Guard (The Eternal Dungeon, Volume 4)
- On Stranger Tides
- On the Beach
- On the Edge of Dream
- On the Parapet
- On the Seas of Destiny
- On the Trail of Dragons
- On the Twelfth Night
- On Wings of Bronze
- On Wings of Magic
- Once a Rake, Always a Rogue
- Once in a Black Moon
- Once Upon a Crown
- Once Upon a Dream
- Once Upon a Fable
- Once Upon a Genie
- Once Upon a Highland Summer
- Once Upon a Magpie Moon
- Once Upon A Prince
- Once Upon a Princess
- Once Upon A Sultan
- Once Upon A Time
- One Bad Man
- One for Sorrow
- One King's Way
- One More Body in the Pool
- One of These Nights
- One Shot
- One Shot, A Talia Sunborn Short Story
- One Thousand
- One Thousand Nights
- Only the Moon: A Short Story Collection
- Only the Stones Survive
- Onyx Rising
- Opening Atlantis
- Operació Gesaleic o Diari d'un viatge
- Operacja Dzień Wskrzeszenia
- Operation "The Black Thunder"
- Operation Castus
- Ophelia
- Opičí král
- Optimizing Family
- Or Even Eagle Flew
- Oracoli
- Orb Sceptre Throne
- Oriente de perla
- Origin
- Original Sin
- Original Sinner
- Origins